1. Field
Aspects of the present invention relate to a porous carbonaceous composite material, a positive electrode and a lithium air battery including the porous carbonaceous composite material, and a method of preparing the porous carbonaceous composite material. More particularly, aspects of the present invention relate to a porous carbonaceous composite material including an oxygen functionalized carbon nanotube (CNT) and a modified carbonaceous material doped with a heterogeneous element and having upward of about 2 atom % of the number of surface oxygen atoms to the number of surface carbon atoms, a positive electrode and a lithium air battery including the porous carbonaceous composite material, and a method of preparing the porous carbonaceous composite material.
2. Description of the Related Art
A lithium air battery generally includes a negative electrode capable of intercalating and deintercalating lithium ions, a positive electrode that oxidizes or reduces oxygen present in the air, and an electrolyte disposed between the negative and positive electrodes.
Since a lithium air battery uses lithium metal as a negative electrode and does not have to store air acting as a positive active material (in detail, oxygen in air) within the battery, the lithium air battery may have high capacity. Lithium air batteries have high theoretical energy densities per unit weight of 3500 Wh/kg or greater, which are about ten times higher than those of lithium ion batteries.
However, because of polarization generated during charging and discharging, existing lithium air batteries have considerably lower energy efficiency compared to lithium ion batteries. To lower the polarization, various kinds of catalysts have been used in the lithium air batteries; however, effects thereof have not been sufficient. For example, “Electrochemistry Communications 13 (2011) 668-672” discloses a lithium air battery including a positive electrode including a carbon nanotube (CNT) doped with nitrogen (N); however, its energy efficiency is also low.
Therefore, there is a demand for methods that further reduce the polarization to obtain higher energy efficiency in a lithium air battery.